Changes in hamstring flexibility and muscle strength during the menstrual cycle in healthy young females.
Manabu Miyazaki, Seiji Maeda
PMID 35221510WHAT IT FOUND
Passive stiffness decreased during ovulation, but muscle strength did not drop.
Range of motion increased in the ovulation and luteal phases compared with the follicular phase. Strength increased in the luteal phase compared with ovulation.
Key findings
01Passive stiffness decreased significantly during the ovulatory phase compared with the follicular phase.
02Isometric muscle force did not show any significant difference between the follicular and ovulatory phases.
03There was a significant increase in isometric muscle force in the luteal phase compared with the ovulatory phase.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study did not measure actual estrogen or progesterone levels, relying instead on calendar and ovulation kits to identify phases. Participants were healthy, non-trained females, so results may not apply to athletes or those with regular training habits. Six of the 22 recruited females were excluded because they did not show clear ovulation signs or temperature patterns, leaving a small sample of 16. Measurements were not randomized; all females were tested in the same chronological order, which could introduce learning effects.
Declared interests
Supported by JSPS KAKENHI. Authors declared no conflicts of interest.
The easy way to misread this
Do not conclude that menstrual cycle fluctuations impair hamstring strength. Although passive stiffness decreased during ovulation, isometric muscle force did not significantly change compared to the follicular phase.